Microbes and Your Food

Foodborne disease-causing organisms that cause illness are numerous and varied, with symptoms ranging from relatively mild discomfort to very serious, life-threatening illness. The very young, the elderly, and people with weakened immune systems are at greatest risk of serious consequences from most foodborne illnesses, howvever some organisms pose grave threats to all everyone. To ensure food is free from microbes, extensive testing in undertaken.

Common Microbes Causing Foodborne Illness

Bacillus cereus

Causes B. cereus food poisoning which appears 10-16 hrs after ingesting contaminated food sources such as meats, stews, gravies, and vanilla sauce. Causes abdominal cramps, watery diarrheoa, and nausea. Lasts 24-48 hours.

Campylobacter jejuni

Causes Campylobacteriosis which appears 2-5 days after ingestion of raw and undercooked poultry, unpasteurized milk, or contaminated water. Causes diarrheoa, cramps, fever, and vomiting. The diarrheoa may be bloody. Lasts 2-10 days.

Clostridium botulinum

Causes Botulism which appears 12-72 hours after ingesting improperly canned foods, especially home-canned vegetables, fermented fish, and baked potatoes in aluminum foil. Causes vomiting, diarrheoa, blurred vision, double vision, difficulty in swallowing, and muscle weakness. Can result in respiratory failure and death. Duration of symptoms varies.

Cronobacter sakazakii

Cronobacter sakazakii is a bacterium that causes a rare but often fatal infection of the bloodstream and central nervous system. Infants with weakened immune systems, particularly premature infants, are most likely to contract an Cronobacter infection, although the bacteria have caused illnesses in all age groups.

Cronobacter sakazakii in Infant Formula

Most cases of Cronobacter sakazakii come from powdered infant formula contaminated with the bacterium. However, this type of infection is still very rare. High temperatures reached in preparing the formula usually kill the bacteria, but they are known to survive even after preparation.

Powdered infant formula is most likely contaminated after production, since the pasteurisation process is normally adequate to kill Cronobacter sakazakii bacteria. However, if the powder is produced using the dry blending process, and not heated, Cronobacter bacteria can survive in the formula.

Symptoms include poor feeding response, irritability, jaundice, grunting while breathing and unstable body temperature in infants, and the infection can lead to meningitis.

Listeria monocytogenes

Causes Listeriosis which appears 9-48 hrs for gastro-intestinal symptoms or 2-6 weeks for invasive disease after ingesting unpasteurized milk, soft cheeses made with unpasteurized milk, or ready-to-eat deli meats. Symptoms include fever, muscle aches, and nausea or diarrheoa. Pregnant women may have mild flu-like illness, and infection can lead to premature delivery or stillbirth. The elderly or immunocompromised patients may develop bacteremia or meningitis. Duration of symptoms varies.

Staphylococcus aureus

Causes Staphylococcal food poisoning which appears 1-6 hours after ingestion of unrefrigerated or improperly refrigerated meats, potato and egg salads, or cream pastries. Symptoms include sudden onset of severe nausea and vomiting, abdominal cramps and diarrheoa and fever may be present. Lasts 24-48 hours.


Cause Salmonellosis which appears 6-48 hours after ingestion of contaminated eggs, poultry, meat, unpateurized milk or juice, cheese, raw fruits and vegetables. Symptoms include diarrheoa, fever, abdominal cramps, and vomiting. Lasts 4-7 days.


Causes Shigellosis or Bacillary dysentery which appears 4-7 days after ingesting contaminated raw produce, drinking water, uncooked foods and cooked foods that are not reheated after contact with an infected food handler. Symptoms include abdominal cramps, fever, and diarrheoa. Stools may contain blood and mucus. Lasts 24-48 hrs.